Double-negative T cells from MRL-lpr/lpr mice mediate cytolytic activity when triggered through adhesion molecules and constitutively express perforin gene.

The lpr gene induces in mice, accumulation of large numbers of CD4-CD8- (double negative [DN]) T lymphocytes which bear adhesion molecules not characteristic of normal resting T cells. These cells fail to acquire interleukin 2 (IL-2) receptors, produce IL-2, and proliferate when activated with mitogens or monoclonal antibodies (mAbs) against the T cell receptor (TCR). Because of these poor functions in vitro, the nature and significance of DN T cells in the autoimmune disease process is not clear. In the current study, we describe a surprising finding that mAbs against CD3-TCR-alpha/beta complex can strongly trigger the lytic activity of the DN T cells to induce redirected lysis of Fc receptor-positive targets. Similar redirected lysis was also inducible using mAbs against CD44 and gp90MEL-14, molecules involved in the binding of lymphocytes to endothelial cells. The spontaneous cytotoxic potential of the DN T cells was further corroborated by demonstrating that the lpr DN T cells constitutively transcribed perforin gene but failed to express granzyme A. The current study suggests that DN T cells are capable of mediating lysis of autologous cells bearing the specific ligands for adhesion molecules involved in the signaling of cytotoxicity. These findings provide a novel insight into the functional significance of DN T cells in lpr mice and their potential role in the pathogenesis of autoimmune disease.

Motility of macrogamonts of Eimeria magna (Coccidia) in cell culture.

Amoeboid movement of spheroid or ovoid immature or mature macrogamonts within cultured Madin-Darby bovine cells usually began with the formation of a pseudopodium-like protrusion at the margin of the gamont. The protrusion enlarged as the gamont cytoplasm and nucleus moved into the protruded area. During movement, macrogamonts had an elongate shape. The body of the gamont was constricted as it moved through the cell cytoplasm or from one cell to an adjacent one. After movement had ceased, the gamont resumed its ovoid or spheroidal shape.

The fine structure of the developmental stages of the microsporidian Nosema apis Zander.

Schizonts, sporonts and sporoblasts of Nosema apis from honey bees collected in the summer and winter were studied with the electron microscope. The nuclei usually had a diplokaryon arrangement. Intranuclear spindles with polar vesicles were associated with division. Schizonts had a single limiting unit membrane, whereas sporonts had a two-layered wall. Sporonts from summer bees had only a thin single limiting membrane in some areas and evidence of endocytosis was sometimes seen in these. Sporonts from winter bees had branched tubular outpocketings from the wall. In sporoblasts, the development of the polar filament was closely associated with a network of dense structures interwoven with a system of tubules evidently of ER derivation; the Golgi complex was associated with this network.